Focus on three main areas: Corrosion, Deformation, and Welding. Check for pitting corrosion which compromises wall thickness; a reduction of more than 10% of the original wall thickness is usually a cause for rejection. Inspect for bends, dents, or cracks in the tubes and ensure that locking pins, couplers, and base plates operate smoothly. For galvanized steel, verify the zinc coating thickness to estimate remaining service life. It is highly recommended to request a video inspection or a live factory walkthrough to see the sorting process.